Mechanical, thermal, and dielectric properties of glass mullite composites for low‐temperature cofired ceramic and radome applications

Abstract

SiO2‐Al2O3‐CaO‐based glass (10–60 wt%)/mullite composites were investigated for the LTCC and radome applications. The optimum densification temperatures decreased from 1550°C (10 wt% glass) to 1400°C (30 wt% glass) by means of liquid‐phase sintering, and to 850°C–825°C (50–60 wt% glass) by means of viscous phase sintering. XRD analysis showed that mullite was the main phase as well as in situ crystallized anorthite after 825°C. The composite with 20 wt% glass was a suitable candidate for the radome applications (bulk density = 2.86 g/cm3 after sintering at 1450°C, dielectric constant (loss) = 7.12 (0.0025) at 5 MHz, thermal expansion coefficient = 4.27 ppm/°C between 25°C and 800°C, thermal shock resistance parameter = 162°C), and the composite with 50 wt% glass was a suitable candidate for the low‐temperature cofired ceramic applications (bulk density = 2.64 g/cm3 after sintering at 850°C, dielectric constant (loss) = 6.79 (0.0043) at 5 MHz, thermal conductivity = 2.11 W/m⋅K at 25°C, and thermal expansion coefficient = 3.93 ppm/°C between 25°C and 300°C).

Effect of complex nucleating agents on crystallization behavior of CaO–Al2O3–SiO2–ZnO–Na2O–K2O glass‐ceramics

“…Adding glass modifiers (e.g., Na 2 O, K 2 O, ZnO, BaO, etc.) to CAS glass lowers its melting point and stabilizes its thermal characteristics, making it applicable in ceramic industry 6–9 …”

Investigation into the effect on the property of Na₂WO₄ ceramic prepared by the further modified solid-state reaction method

“…5), 6) With the decrease of the sintering temperature of LTCC, it has been proven that the PVA cannot be decomposed totally and the residue affects the property of the ceramic sample. 7), 8) More than that, the granulation course is not a very detailed process, which means the quality of granulation is largely related to the experimenter. The particle fluidity affects the compactness of the green ceramic body to a great extent.…”